Method of and system for communication by radiant energy



Nov. 30 1926. 1,609,116

J. H. HAMMOND, JR

METHOD OF AND SYSTEM FOR COMMUNICATION BY RADIANT ENERGY Filed August 17., 1922 s Sheets-Sheet 1 I I I I i I? I I Nov; 30,1926. 1,609,116 J. H. HAMMOND, JR

METHOD 3F AND SYSTEM FOR COMMUNICATION BY RADIANT ENERGY Filed August 17, 1922 V 3 Sheets-Sheet 2 & WV- non Nov. 30 1926. 1,609,116

J. H. HAMMOND, JR

METHOD OF. AND SYSTEM FOR COMMUNICATION BY RADIANT ENERGY Filed August 17, 1922 5 Sheets-Sheet 5 avwentoz Jab/7 figs/212021011407. 92, his flaw, I

Patented Nov. 30, 1926,,

untrue stares JOHN HAYS HAMMOND, JR" 01 GLOUCESTER, MASSACHUSETTS.

METHOD OF AND SYSTEM FOR COMIEUNICATION RADIANT ENERGY.

Application filed August 17, 1822.

This invention relates to methods of and systems for communication by radiant energ-y.

Some of the objects of the present invention are to provide an improved system for the transmission of intelligence; to provide an improved receiving station adapted to be selectively responsive to energy of complex wave form; and to provide for the reception of oscillatory energy of complex wave form by producing beats with the received Waves. Still other objects of the invention will ap pear from the following description taken in connection with the accompanying drawings, in which,

Figure 1 is a diagram of a sending station which embodies features of the invention; Figure 2 is a diagram of a receiving station arranged to cooperate with the sending station of Figure 1; and Figure 3 is a diagram of a modified form of receiving station.

The system illustrated in the drawings as one embodiment of the present invention employs at its sending station a carrier wave of relatively high frequency, upon which are impressed amplitude variations of relatively lower but supersonic frequency, the fre quency of the amplitude variations being changed in accordance with signals.

111 a general way, the receiving station may be described as comprising a plurality of resonant circuits in series, a hete'rodyne for producing; beats of supersonic, frequency with the received waves, a detector for producing from the beats oscillations of a frequency corresponding to the frequency of the amplitude variations of the waves, a second heterodyne for producing beats with the oscillations, and detecting and indicating means for the last-mentioned beat currents. By varying slightly the frequency of the amplitude variations in accordance with a signal, differently characterized beat currents may be produced, the changes in the beat currentcorresponding, to the signal.

Referring more in detail to the drawings, the sending station shown in Figure 1 includes a source of hi gh frequency oscillations in the form of a suitable thermionic device 10 having a filament 11 for emitting electrons, a plate 12 upon Which the electrons impinge, and a grid 13 for controlling the passage of the electrons. These parts are connected with interrelated, inductively- Serial No. 582,341.

coupled circuits in such a manner that the energy in the plate circuit reacts on the grid circuit so as to cause the device to oscillate regeneratively. There is thus produced an oscillatory current of a relatively high frequency, the frequency being determined by the electrical constants of the inter-related circuits.

For producing oscillations of relatively lower but supersonic frequency, there is provided a second thermionic device 20, having a usual filament 11, plate 12 and grid 13. These parts are coupled for regeneration by means of a transformer 21 having windings 22, and 24. The windings 22 and 23 are connected in the plate and grid circuits of the device 20. respectively. This regenerative circuit arrangement is provided with a pair of condensers and 26 in series, the total capacity of which determines in part the frequency of the oscillations generated by the oscillator 20.

For impressing'these oscillations upon the waves produced by the radio oscillator 10, the winding 24L of the coupling); transformer 21 is connected by conductors 30 and 31 in the input circuit of the oscillator 10. The waves generated by the oscillator 10 are thus modulated at a relatively-lower frequency, which may be supersonic, in a manner such that there appears in the output of the radio oscillator a complex wave having periodic variations in amplitude, these variations corresponding in frequency to that of the oscillator 20.

For emitting these waves from the sendinp; station, there may be provided, for example, an antenna LO'WhOSG circuit includes a winding 41 of transformer 42. Other windings 43 and 4A of the transformer 42 are inductively coupled to the winding 41 and to each other. For varying the frequency of the amplitude variations of the emitted energy, there is provided a signal transmitter which in the present instance takes the form of a key or contact-making device connected in shunt with the condenser 26 so as to vary the capacity of the circuit of the generator 20, and thus vary the frequency of the pe-, riodic variations produced thereby.

The receiving set of Figure 2 comprises a receiving element positioned so as to intercept Hertzian waves, such as an antenna 50. The circuit of the antenna 51' includes a iii winding of a coupling 51, whose other winding forms part of a usual, closed, oscillatory circuit 52, and a winding of a second coupling 53, whose other winding is in circuit with a. source of oscillatory energy such as an alternator 54. The coupling 53 and alternator 54 form collectively a so-called heterodyne for producing oscillatory energy differing from the intercepted or received energy and thus causing beats in a well known manner. The frequency of the bet erodyne 53, 54 in the present instance differs from that of the waves transmitted, i. e., that of the radio oscillator 10, by an amount greater than the frequency of the periodic variations produced by the oscillator 20.

The closed, oscillatory circuit 52 is tuned broadly to the carrier wave and to the frequency of the heterodyne 53, 54, and the energy set up therein is rectified or otherwise detected by a suitable detector 60. The output circuit of the detector 60 includes winding 61 of an interstage transformer 62, shunted by a lay-pass condenser 63, and

there is thus induced in the secondary winding 64 of the transformer 62 a current having the frequency and characteristics of the beat current resulting from combining the received energy with that of the heterodyne 53, 54. These beat currents have impressed upon them the amplitude variations which were impressed upon the emitted energy at the sending station. An adjustable con denser 65 forms with the secondary wind-' ing 64 a closed oscillatory circuit 66 which is broadly tuned to be responsive to the several frequencies or band of frequencies produced by combining energy from the local source 54 with the received energy and detecting the beat currents.

For example, with an A frequency of the radio oscillator of say 1,000,000 cycles per second, modulated at a B frequency generated by the oscillator of say 20,000 cycles per second when the key is open and 19.000 cycles when the key 50 is closed, and a frequency of say 1,100.000 cycles per second generated by the heterodyne 54;. the beat currents in the oscillatory circuit 52 will be 100.000 cycles per second. with variations of the frequency of 20,000 or 19,000 impressed thereon, and the circuit 66 is tuned to respond to such modulated currents.

For rectifying or otherwise detecting the energy set up in the oscillatory circuit 66 so as to produce current corresponding in frequency to its component of lower frequency, that is, the variations impressed upon the received energy, there is provided a detector -70, which may take any suitable form. The output circuit of the detector 7 0 includes a winding 71 of a transformer 72, with a usual by-pass condenser 73. There is thus induced in the winding 74 of the transformer 72 a current having the frequency and characteristics of the amplitude variations which were impressed by the sender on the emitted energy. The winding 74 of the transformer 72 in combination with an adjustable condenser 75 forms closed, oscillatory circuit, tuned to respond to the B or variation frequencies employed, assumed in the present instance cited, by way of example, to be 20,000 and 19,000 per second.

For producing oscillations in the winding 74 which will differ somewhat from the l) frequency so as to produce a readily distinguishable signal or indication, there may be provided a suitable means such as a local alternator in circuit with a suitable winding 81 of the transformer 72, thus forming a heterodyne. An indicating device 82, hav ing a by-pass condenser 83, is provided in the circuit of the winding 74 for reproducing the signals sent by the transmitter. The device 82 may take the form of a telephone receiver, and there is provided in its circuit suitable detecting means, such as a detector 84. If this detector is of the amplify-- ing type such as a. three-electrode thermionic vacuum tube, its output circuit may be connected in circuit with the winding 81 to produce an autodyne. In such case, the heterodyne generator 80 may be omitted.

In the modified form of the invention shown in Figure 3, the windings 61 and (54 of Figure 2 are coupled to one another through suitable amplifying means instead of directly. As shown, a pair of three-elec-- trode thermionic vacuum tubes 101 and 102 are provided in cascade, interconnected by means of an inter-valve transformer 103. A winding 104 included in the input circuit of the first amplifying tube of the series is i iductively coupled to the winding 61, and similarly a winding 105 included in the output circuit of the last amplifying tube is inductively coupled to the winding 64. Suitable filament heating batteries 100 and 107 and plate potent a... batteries 108 and 109 may be provided in a well known man ner; Any desired number of amplifying tubes may be employed to provide a desired 1 degree of amplification.

In the operation of the system described, the sender impresses on the ether when the key 50 is open. energy having the form of oscillations of a fundamental or A frel quency, of, for example. 1.000.000 cycles per second, modified or modulated by variations having B frequency of say 20,000 cycles per second. hen the key 50 is closed. the emitted energy has the form of oscillations of the same fundamental or A frequency. that is 1,000,000 cycles with a B frequency of, for example. 19,000 cycles per second. These waves are intercepted by the receiving element or antenna 50, and the funda ill till

mental frequency beatswith the oscillations produced by the heterodyne 54. The resultant beat currents of 100,000 cycles are detected by detector 60.

An important feature of the invention is that the received energy is thus transfo-rn'ied or stepped down to a frequency much less than the radio frequency, and consequently relatively easier to amplify by ordinary ainplifying' devices such as three-electrode thermionic vacuum tubes.

The energy of the beat currents of a frcquency of, for example, 100,000 cycles per second, is imparted to the winding 64 as described in connection with Figure 2, or is amplified and then applied, as described in connection with Figure 3, and is impressed on the detector 70, which produces in its output circuit current of frequency corresponding to that of the component of the B frequency. The frequency produced in the winding 81 is predetermined by suitably operating the alternator 80 or by adjusting the constants of the autodyne circuit, if used, so as to differ slightly from the B frequency. Thus when the B frequency is changed by operating the signal transmitter 50, assuming that the indicating device used is a telephone receiver, a change is made in the tone produced thereby, so as to produce a signal corresponding to that sent by the transmitter 50.

Telephonic messages may be transmitted by employing a sender arranged to vary the amplitude of the periodic variations by means of voice waves. The receiving station of Figure 2 or Figure 3 may be em ployed to transform or step down the frequency of the. intercepted energy for convenient amplification and detection.

Various other modifications may be made without departing from the spirit of the invention; and it is therefore understood that the scope of the invention is not to be limited to the specific disclosures selected for illustration, but that reference is to be made to the appended claims for that purpose.

What is claimed is:

1.. A system of signalling comprising means for producing energy having the form of oscillations of high frequency. means for impressing periodic variations of relatively lower but supersonic frequency on the high frequency oscillations, means for varying the frequency of the variations in accordance with a signal, and a receiving station having means responsive to said energy, means for transformingsaid energy into oscillations having a frequency intermediate between the frequency of said high frequency oscillations and the frequency of said variations, and means for detecting and indicating the oscillations to produce a signal.

2. A system of signalling comprising means for producing energy having the form of oscillations of high frequency, means for impressing periodic amplitude variations of relatively lower but supersonic frequency on the high frequency oscillations, means for varying the energy in accordance with a signal, and a receiving station having means responsive to said energy, means for stepping down said energy into oscillations having a frequency intern'iediate between the frequency of said high frequency oscillations and the frequency of said variations, and

means for detecting and indicating the oscillations to produce a signal.

3. A system of signalling comprising means for producing energy having the form of oscillations of high frequency, means for impressing amplitude variations of relatively lowerbut supersonic frequency on the high frequency oscillations, means for varying the energy in accordance with a signal, and a receiving station having means responsive to said energy, means for transforming. said energy into oscillations having a frequency intermediate between the frequency of the high frequency oscillations and the frequency of said variations, an amplifier for amplifying the oscillations, and means for detecting and indicating the oscillations to produce a signal.

4. In a system of signalling, a receiving station for receiving the energy of a wave of a predetermined, high frequency modulated by periodic variations of lower frequency, including a heterodyne for pro ducing beats with the received energy, the frequency of the beats being above the frequency of the variations, a demodulator for producing from the beat current oscillatory energy having the frequency of the variations, and means for detecting and indicating said oscillatory energy.

5. A system of signalling comprising a sender and a receiver, said receiver includ ing an indicating device, the sender being arranged to emit energy in the form of high frequency oscillations modified periodically by variations at a rate lower than the frequency of the first-named oscillations but above the rate of responsiveness of said indicating device, a signal transmitter for modifying the energy, means for producing at the receiver current of a frequency intermediate between that of the high frequency oscillations and that of said variations, means for producing from said firstmentioned current oscillatory energy of the frequency of said variations and means for producing from said oscillatory energy current which will operate the indicating device.

6. Apparatus for receiving the energy of a series of waves of high frequency modulated by variations of lower, but supersonic, frequency comprising means responsive to said energy, means for transforming said energy into oscillations having a frequency intermediate between said first-mentioned frequencies, and means for detecting and indicating said oscillations to produce a signal.

7. Apparatus for receiving the energy of a series of waves of high frequency modulated by variations of lower, but supersonic, frequency comprising means responsive to said energy, means for hetcrodyning said energy to produce oscillations having a frequency intermediate between said firstmentioned frequencies and modulated by said variations, and means for detecting and indicating said oscillations to produce a signal.

8. Apparatus for receiving the energy of a series of waves of high frequency modulated by variations of lower, but supersonic, frequency comprising means responsive to said energy, means for transforming said energy into oscillations having a frequency intermediate between said first-mentioned frequencies, an amplifier for amplifying said oscillations, and means for detecting and indicating the oscillations to produce a signal.

9. Apparatus for receiving the energy of a series of waves of high frequency modulated by periodic variations of a frequency lower than the frequency of the waves but above good audibility, comprising in .combination a heterodyne for producing beat currents with the received energy, means for producing from the beat currents oscillatory energy having the frequency of said variations but differing from the beat frequency, means for producing currents of good audibility from said oscillatory ener gy, and means for indicating said last-mentioned currents.

10. Apparatus for receiving the energy of a series of waves of high frequency modulated by amplitude variations of lower frequency comprising means. for. hetcrodyning the received energy to produce current of a beat frequency higher than the frequency of the variations, closed, oscillatory circuits responsive respectively to currents of the beat frequency and of the frequency of the variations, means interposed between said circuits for producing current corresponding in frequency to said variations from said beat frequency urrent, and means for detecting and indicating the energy set up in said last-mentioned circuit.

11. The method of signalling which con sists of producing and emitting energy having the formof oscillations of high frequency modulated by variations of lower but supersonic frequency, changing the frequency of the modulating oscillations, receiving the energy at a remote station, lowering the frequency to a frequency above that of the modulating variations, selecting the modulating component, and detecting and indicating said component to reproduce the signal.

12. The method of signalling which consists of producing and emitting energy having the form of oscillations of high fre quency modulated by amplitude variations of lower but supersonic frequency, chang ing the frequency of the modulating oscillations, receiving the energy at a remote station, lowering the frequency to a fre quency above that of the modulating variations, amplifying the received energy at said lowered frequency, selecting the modulating component and detecting and inclicating said component to reproduce the signal.

13. The method of signalling which consists in producing and emitting energy having the form of oscillations of high frequency modulated by amplitude variations of lower but supersonic frequency, modifying the energy in accordance with signals, receiving the energy at a remote station, hetcrodyning the received energy to produce current of a beat frequency higher than the frequency of the variations, producing from the beat frequency current oscillatory energy corresponding in frequency to said variations and detecting and indicating the oscillatory energy to reproduce the signals.

In testimony whereof, I hereunto affix my signature.

JOHN HAYS HAMMOND, JR.

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